Light has been studied for centuries by many scientists, the most notable of them being Aristotle, Galileo, Albert Michelson, and Albert Einstein. It was once thought by ancient scientists that light was produced from our own eyes and sent forth to the object we looked at. This was, of course, later disproved when it was determined that our sight depends on light reflecting off of other objects and reaching our eyes rather than our eyes producing the necessary light. Other theories about light such as the particle theory, wave theory, and an infinite light-speed were also put to the test. The particle theory stated that light was traveled in particles while the wave theory said it was traveled in waves.The wave theory became the accepted theory in the 1800s due to the works of post-Newton era scientists. There was much debate as to the composition of light for quite some time until Albert Einstein published his theory on the photo-electric effect explaining that light was composed of particles, now called photons. It is generally accepted that light is both particle and wave, though it is still strongly disputed either way since light acts like a particle in some situations, and a wave in others. Through countless experiments light was determined to have a finite speed, around 300,000 kilometers per second, and to be part of the range of electromagnetic waves which we commonly refer to as light.
Electromagnetic Waves
Electromagnetic waves are the product of an overlap between an electric field and a magnetic field.
Visible light is but a small part of the whole light spectrum and is composed of a series of electromagnetic waves which are a part of the electromagnetic spectrum. The electromagnetic spectrum is composed of a wide range of waves at various frequencies of which light as a whole is but a small part of. The different types of light waves are radio waves, microwaves, infrared, visible/optical, x-rays, and gamma rays.
Radio waves are the longest of the electromagnetic waves. The typical sources of radio waves in the universe are stars, galaxies, and even hydrogen atoms. Microwaves are left over radiation from the big bang. Like radio waves, microwaves can be detected with a radio telescope. Infrared light is heat absorbed and re-emitted by particles and is in the part the spectrum lower than red light. Ultraviolet light is on the end lower than violet light and is energy that radiates from stars. Of all the light types, visible or optical light is the only portion of the electromagnetic spectrum visible to the naked human eye. We see these waves as the colors of the rainbow - red, orange, yellow, green, blue, and violet which can be seen through use of a prism. Rainbows are formed when atmospheric water vapor performs this neat prism trick. Each color correlates to a different wavelength which is expressed in nanometers(nm). The individual colors in white light can be seen when light is shone through a prism, a trick first discovered by Sir Isaac Newton. X-rays, also known as Roentgen rays, are high energy waves with short wavelengths that were first discovered accidentally by Wilhelm Conrad Roentgen in 1895. These rays are given off during high energy occurrences such as matter falling into a black hole. The last type of light, gamma rays, have the shortest wavelength and possess the largest amount of energy of all of the light waves. Gamma rays are a form of radiation given off during extremely energetic events such as supernovas. These rays are so powerful they can lead to the death of living cells which is why gamma radiation is used as a cancer treatment. 471213
Image Courtesy of UN Energy
Image courtesy of The Physics Classroom
Light Speed
Many experiments have been conducted through the centuries to determine the speed of light. Of course the first step of that was figuring out whether light moved at an infinite speed or was constant. Near 1675, Olaus Roemer, a Danish scientist, proved light had a finite speed by measuring the revolution periods of Jupiter's moon Io and finding a difference in the revolution time relative to the Earth's position in regards to Jupiter. When Earth was farther away the moon seemed to be delayed when passing through Jupiter's shadow, but scientist Christian Huygens found out that the light itself was late, not the moon. Galileo Galilei attempted to measure the speed of light using a mirror. The point of the experiment was to discover the time it took light to reach the mirror in the distance and back. Unfortunately, the experiment was unsuccessful. A somewhat similar test was conducted by Albert Michelson in 1880 using a mirror on a mountaintop, a spinning octagonal mirror, and a telescope. In this experiment he eventually determined that light took 1/8 of the octagonal mirror's spin to make a trip to the mountain and back. He calculated that the speed of light was 299,920 km/s, a number which is typically rounded to 300,000 km/s.
In a vacuum, light travels at approximately 300,000 km/sec, or 186,000 m/sec. It travels at this speed in a vacuum because light can be slowed down when passing through solid objects. The speed of light in a vacuum, known as the constant (c), was determined to be the fastest speed in the universe. This is so because of Einstein's famous special theory of relativity, well-known for its equation E=mc². It basically states that mass can be converted into large amounts of Energy. Therefore, when an object approaches the speed of light, it gains more mass and therefore needs more energy to maintain that speed. This is why only light, a "mass-less" thing can approach this speed. Einstein's theory of relativity also says that light speed is constant throughout the universe and the speed of light is the same for all observers.1236
In reference to light interactions, there are three types of material in the world: transparent, translucent, and opaque. Light passes through transparent materials completely with no affect on the light, it's as if the item was never there to begin with. Transparent materials are things such as glass, air, and water (in certain situations). Translucent materials are items that light can travel through but the light is diffused, or scattered, as a consequence, preventing a clear image of the object(s) on the other side of the material. An example of a translucent item is frosted glass or water, both of which distort the image.
Opaque materials absorb light instead of remitting it as translucent and transparent objects do. Examples of opaque items are metals, wood, and humans.
Materials fall into these different categories because of the interaction between the frequency of the vibration of a material and the light's vibration due to their respective natural electron frequencies. For example, metals appear to be shiny because their electrons vibrate and give off their own light waves in response to contact with a ray of light.
A well-known light interaction is that of the shadow. Shadows are created in places where light cannot reach. As an example, imagine a lamp sitting on a desk against the wall while turned on. The lighted part of the wall is directly above the lamp and fans out a little while the rest of the wall is dark. The dark part is in shadow because the light cannot reach that area.
There are two types of shadows: the penumbra and the umbra. An umbra is a complete shadow, typically caused by a ray of light from a small source shining on an object. The penumbra is not a total shadow and happens when light from a large source is not completely blocked or when the light is blocked but light from other sources fills in the shadow. A much larger scale example of shadow is a solar eclipse. A solar eclipse occurs when the moon travels between the Earth and the Sun. 811
Polarization
Polarization occurs when a wave moves back and forth in a single direction- up and down, which would be vertical, or left to right, which would be horizontal. The direction of polarization is determined by electrons. If an electron vibrates vertically, then an vertically polarized electromagnetic wave is produced. If an electron vibrates horizontally, a horizontally polarized wave is produced.
Not all light sources emit polarized light. Sources whose electrons vibrate in different, or random, directions do not give off polarized light. But, there is a way to polarize light, four ways in fact:
Directing a ray of light through a polarizing filter blocks one of the two planes of vibration. Polarizing filters are commonly used in photography to get rid of some of the reflected light, or glare, on glass, metal, or liquid surfaces in a picture.In photographs featuring water such as a picture of the ocean or a waterfall, the water appears to be more transparent without the glare.In addition to cameras, polarizing filters are also used in sunglasses.
Refraction, which occurs when a wave, in this case light, is bent when passing through one material into another is a cause of polarization.
When light particles are scattered the light can become polarized. When light passes through a material it can come into contact with the atoms of said material. When this occurs the light ray's electrons begin vibrating and unleash a domino effect- each of the electrons begin vibrating in the same direction as its neighbor.
Reflection- when light reflects off of nonmetallic surfaces it is polarized on the same plane as the item it was reflected off of. The level of polarization that occurs is determined by the angle that the light reaches the surface at and what the surface itself is made of. 514
Table of Contents
Light
Light has been studied for centuries by many scientists, the most notable of them being Aristotle, Galileo, Albert Michelson, and Albert Einstein. It was once thought by ancient scientists that light was produced from our own eyes and sent forth to the object we looked at. This was, of course, later disproved when it was determined that our sight depends on light reflecting off of other objects and reaching our eyes rather than our eyes producing the necessary light. Other theories about light such as the particle theory, wave theory, and an infinite light-speed were also put to the test. The particle theory stated that light was traveled in particles while the wave theory said it was traveled in waves.The wave theory became the accepted theory in the 1800s due to the works of post-Newton era scientists. There was much debate as to the composition of light for quite some time until Albert Einstein published his theory on the photo-electric effect explaining that light was composed of particles, now called photons. It is generally accepted that light is both particle and wave, though it is still strongly disputed either way since light acts like a particle in some situations, and a wave in others. Through countless experiments light was determined to have a finite speed, around 300,000 kilometers per second, and to be part of the range of electromagnetic waves which we commonly refer to as light.
Electromagnetic Waves
Electromagnetic waves are the product of an overlap between an electric field and a magnetic field.
Visible light is but a small part of the whole light spectrum and is composed of a series of electromagnetic waves which are a part of the electromagnetic spectrum. The electromagnetic spectrum is composed of a wide range of waves at various frequencies of which light as a whole is but a small part of. The different types of light waves are radio waves, microwaves, infrared, visible/optical, x-rays, and gamma rays.
Radio waves are the longest of the electromagnetic waves. The typical sources of radio waves in the universe are stars, galaxies, and even hydrogen atoms. Microwaves are left over radiation from the big bang. Like radio waves, microwaves can be detected with a radio telescope. Infrared light is heat absorbed and re-emitted by particles and is in the part the spectrum lower than red light. Ultraviolet light is on the end lower than violet light and is energy that radiates from stars. Of all the light types, visible or optical light is the only portion of the electromagnetic spectrum visible to the naked human eye. We see these waves as the colors of the rainbow - red, orange, yellow, green, blue, and violet which can be seen through use of a prism. Rainbows are formed when atmospheric water vapor performs this neat prism trick. Each color correlates to a different wavelength which is expressed in nanometers(nm). The individual colors in white light can be seen when light is shone through a prism, a trick first discovered by Sir Isaac Newton. X-rays, also known as Roentgen rays, are high energy waves with short wavelengths that were first discovered accidentally by Wilhelm Conrad Roentgen in 1895. These rays are given off during high energy occurrences such as matter falling into a black hole. The last type of light, gamma rays, have the shortest wavelength and possess the largest amount of energy of all of the light waves. Gamma rays are a form of radiation given off during extremely energetic events such as supernovas. These rays are so powerful they can lead to the death of living cells which is why gamma radiation is used as a cancer treatment. 4 712 13
Light Speed
Many experiments have been conducted through the centuries to determine the speed of light. Of course the first step of that was figuring out whether light moved at an infinite speed or was constant. Near 1675, Olaus Roemer, a Danish scientist, proved light had a finite speed by measuring the revolution periods of Jupiter's moon Io and finding a difference in the revolution time relative to the Earth's position in regards to Jupiter. When Earth was farther away the moon seemed to be delayed when passing through Jupiter's shadow, but scientist Christian Huygens found out that the light itself was late, not the moon. Galileo Galilei attempted to measure the speed of light using a mirror. The point of the experiment was to discover the time it took light to reach the mirror in the distance and back. Unfortunately, the experiment was unsuccessful. A somewhat similar test was conducted by Albert Michelson in 1880 using a mirror on a mountaintop, a spinning octagonal mirror, and a telescope. In this experiment he eventually determined that light took 1/8 of the octagonal mirror's spin to make a trip to the mountain and back. He calculated that the speed of light was 299,920 km/s, a number which is typically rounded to 300,000 km/s.
In a vacuum, light travels at approximately 300,000 km/sec, or 186,000 m/sec. It travels at this speed in a vacuum because light can be slowed down when passing through solid objects. The speed of light in a vacuum, known as the constant (c), was determined to be the fastest speed in the universe. This is so because of Einstein's famous special theory of relativity, well-known for its equation E=mc². It basically states that mass can be converted into large amounts of Energy. Therefore, when an object approaches the speed of light, it gains more mass and therefore needs more energy to maintain that speed. This is why only light, a "mass-less" thing can approach this speed. Einstein's theory of relativity also says that light speed is constant throughout the universe and the speed of light is the same for all observers.1236
Light Speed Clip
9
Light Interactions
In reference to light interactions, there are three types of material in the world: transparent, translucent, and opaque. Light passes through transparent materials completely with no affect on the light, it's as if the item was never there to begin with. Transparent materials are things such as glass, air, and water (in certain situations). Translucent materials are items that light can travel through but the light is diffused, or scattered, as a consequence, preventing a clear image of the object(s) on the other side of the material. An example of a translucent item is frosted glass or water, both of which distort the image.
Opaque materials absorb light instead of remitting it as translucent and transparent objects do. Examples of opaque items are metals, wood, and humans.
Materials fall into these different categories because of the interaction between the frequency of the vibration of a material and the light's vibration due to their respective natural electron frequencies. For example, metals appear to be shiny because their electrons vibrate and give off their own light waves in response to contact with a ray of light.
A well-known light interaction is that of the shadow. Shadows are created in places where light cannot reach. As an example, imagine a lamp sitting on a desk against the wall while turned on. The lighted part of the wall is directly above the lamp and fans out a little while the rest of the wall is dark. The dark part is in shadow because the light cannot reach that area.
There are two types of shadows: the penumbra and the umbra. An umbra is a complete shadow, typically caused by a ray of light from a small source shining on an object. The penumbra is not a total shadow and happens when light from a large source is not completely blocked or when the light is blocked but light from other sources fills in the shadow. A much larger scale example of shadow is a solar eclipse. A solar eclipse occurs when the moon travels between the Earth and the Sun. 811
Polarization
Polarization occurs when a wave moves back and forth in a single direction- up and down, which would be vertical, or left to right, which would be horizontal. The direction of polarization is determined by electrons. If an electron vibrates vertically, then an vertically polarized electromagnetic wave is produced. If an electron vibrates horizontally, a horizontally polarized wave is produced.Not all light sources emit polarized light. Sources whose electrons vibrate in different, or random, directions do not give off polarized light. But, there is a way to polarize light, four ways in fact:
Vocabulary
References